This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We have raised high affinity llama single domain antibodies against GFP, and are currently endeavouring to fully characterize them. Should we be successful in this endeavoour, we will be able to make generally available these important reagents in essentially unrestricted quantities.